338 



MICROSCOPIC ANATOMY OF THE OKf.'JAX 



state (at the end of pregnancy) the alveoli increase in size, nu- 

 merous leucocytes find their way into the lumena of the alveoli, 

 and the granular epithelial cells begin the formation of fat. 

 These fat globules are taken up by the leucocytes, which are 

 thus converted into colostrum corpuscles. After the birth of 

 the child the gland cells become larger and the production of 

 fat increases. The walls of the alveoli now consist of high 

 cylindrical gland cells full of secretion, and also lower cells 

 which have been emptied of their contents. The part of the 



FIG. 258. 



Fat globules 



Membrana propria 



Lumen of acinus 



Tangential section^_ _ 



of acinus "- -^ 



Part of a transverse section of the mammary gland of a guinea-pig during lactation. X 500. 



cell bordering on the lumen especially undergoes fatty change. 

 When this secretion escapes, the part of the cell containing the 

 nucleus regenerates the whole cell. This process may take place 

 many times. The whole cell does not disintegrate, as is the 

 case in the sebaceous glands. Mitotic division is observed 

 often in these cells, while, on the contrary, extruded nuclei 

 are found free in the lumen of the alveolus. 



The membrana propria of the alveolus is homogeneous, 

 and contains on its inner surface stellate basket cells, which 

 surround the gland cells by long processes. 



